The objective of a printed circuit board (PCB) power delivery network (PDN) is to provide a stable supply voltage to the integrated circuits on the PCB. The objective of a PCB signal distribution network (SDN) or data bus is to distribute signals, which are often very high frequency switching signals, among and between the integrated circuits on the PCB. The high frequency switching signals and the current drawn by the switching devices producing those switching signals may induce noise onto the supply voltage carried by the PDN as well as devices on the PCB, such as, for example, sensors. The continuing trends of increasing IC clock and switching speeds induce higher levels of noise on the PDN, and the trend toward reduced IC supply and Input-Output (IO) voltages to increase battery life of mobile devices cause the level of noise that can be tolerated on the supply voltage to shrink. In other words, as supply voltages shrink and as clock/switching speeds increase, IC devices have reduced tolerance for noise on the supply voltage provided by the PDN.
Since the amount of noise that may be induced onto the PDN by the switching signals on the SDN is proportional to the impedance of the PDN, the worst case induced noise levels occur when the switching signals have considerable power content in a frequency that approximates the one or more resonant frequencies of the PDN, since impedance of the PDN peaks at those one or more resonant frequencies. PDN noise may also be problematic at other frequencies at which the PDN has relatively high impedance values. Decoupling capacitors may be added to reduce the degree of coupling between the PDN and the SDN over one or more target frequency bands, requiring the use of a range of values of decoupling capacitors, or the size of the power plane area may be increased, but these approaches undesirably increase the cost and form factor of the PCB.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.